Dormancy is a
general term denoting the non-growing (resting, quiescent or
inactive) phase of plants life or of viable seeds.

Dormancy is a state of low metabolic activity that
occurs during the yearly cycle in plants or seeds when no outwardly
visible growth takes place.
It is a physical or physiological condition that suspends or prevents
growth or germination even in the presence of otherwise favourable
conditions.

It is possible to identify two principal types of
dormancy:

Endodormancy: a period of quiescence caused by conditions or
factor within the plant or organ itself. (For example the winter rest
)

Ectodormancy: ( also Ecodormancy or diapause) (exogenous or
external dormancy ) a period of quiescence caused directly by adverse
conditions, and lasting only while they prevail.

Dormancy affected by :

Photo-period

Environmental induction

Low temperature and effective chilling temperatures
in colder regions

Hot and drought in warmer areas

Phytohormones

Site of the bud and bud differences

Environment and/or cultural practices

Dormancy breaking chemicals

Plant dormancy in temperate zones (the Winter rest) usually takes place
during colder periods when plant leaves have fallen or the top growth
has died down and seeds, buds bulbs or tubers exhibit a lack of growth
or flowering it is a survival strategy which temperate climate species
are generally believed to have to survive winters unfavourable
conditions.
The plant in tropical areas goes dormant especially during
extended hot, dry periods (see dry season)

Seed dormancy is the state of inhibited germination of seeds that
suspends or prevents germination even in the presence of otherwise
favourable germination conditions. The breaking of seed dormancy
requires moisture, sometimes cold temperatures and/or abrasion of the
seed coat. ( see: scarification)

During dormancy many plants require less water, cooler temperatures and
fertilizing should be withheld ( see: overwintering). Dormancy is thus a
good time to transplant or prune some species of plants ( e.g. Trees).